Journal of Electroceramics最新文献

In the present work, tackle the two issues with one single activity resource that strategy has followed. The organic dye methyl orange (MO) and drug ciprofloxacin (CIP) have been effectively degraded by the synthesized ZnO@CuO under visible light irradiation. The hexagonal structured zinc oxide (ZnO), monoclinic structured copper oxide (CuO) and the mixed phase of ZnO@CuO has been prepared by the hydrothermal method. The structural characterization of prepared materials has been analyzed by powder X-ray diffraction (P-XRD) and the Rietveld refinement technique. The surface morphology of synthesized materials has been measured by scanning electron microscope characterization. The luminescence performance of prepared materials has studied by photoluminescence (PL) characterization. The photocatalytic results suggest that the ZnO@CuO composite is the effective candidate of degradation of ciprofloxacin antibiotic drug and methyl orange dye. From the results, ZnO@CuO revealed excellent photocatalytic behavior for CIP and MO degradation under stimulated sun light irradiation with the efficiency of above 95%. In addition, the optimum parameters were analyzed to the degradation process. This type of affordable photocatalyst gives a new beginning for further research studies. In addition, the electron density distribution analysis of synthesized materials has been studied.

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In this work, H₃BO₃ and Bi₂O₃ with the ratio 3:2 were melted at 750 °C and then quenched in water to produce B-Bi-O frit, which was sintered and co-doped with TiO₂-0.60Nb₂O₅-0.50ZnO varistor ceramics. It is found that B-Bi-O frit can reduce the sintering temperature and improve the electrical properties of TiO₂ ceramics. The best comprehensive electrical properties with the nonlinear coefficient up to 8.9, the breakdown voltage down to 4.92 V/mm, the relative dielectric constant of 4.47*10⁵ and the leakage current of 0.102 mA are achieved by sintering the ceramics doped with 3 wt% B-Bi-O frit at 1400 °C. XRD analysis shows that B-Bi-O frit is an amorphous phase, and no second phase can be found in ceramics after the frit is doped. SEM morphologies display that B-Bi-O frit is beneficial to decrease the porosity while increase the grain size, and EDS mapping further presents no elements segregate on the grain boundary. XPS spectra demonstrate the coexistence of Ti³⁺ ions, Ti⁴⁺ ions and oxygen vacancies in TiO₂ ceramics. As a result, it can be concluded that the enhancement of the electrical properties of TiO₂ ceramics is mainly attributed to the following aspects: on the one hand, B-Bi-O frit helps to produce liquid phase sintering, which would reduce the porosity while increase grain size and promote solid solution of Nb₂O₅ and ZnO in TiO₂ ceramic. On the other hand, B and Bi elements can also act as acceptor dopants in TiO₂ ceramic to further promote grain semi-conductivity and increase grain boundary barrier height.

La_0.6Sr_0.4FeO₃ ceramic was elaborated by solid-state route. Preliminary room-temperature structural analysis evidences the sample formation in the orthorhombic structure and its phase purity. Electrical properties of the studied ceramic have been investigated according to dielectric measurements in the frequency range 10^–1 - 10⁶ Hz and the temperature range 93 - 313 K. Electrical conductivity curves exhibit a step-like behavior, at low temperatures, attributed to grain boundaries and grain contributions which are well described by the two Jonscher equations. The grains conduction mechanism is consistent with the thermally activated hopping of small polaron (SPH). Whereas, this mechanism is no longer satisfied for grain boundaries conduction mechanism at lower temperatures. Indeed, this latter is governed by the variable range hopping (VRH) model. This electrical conductivity analysis is further confirmed by the complex impedance formalism according to the obtained activation energies. Analysis of Nyquist plots at low temperatures has evidenced the presence of two grain boundaries effects attributed to the heterogeneous structure of La_0.6Sr_0.4FeO₃ grain boundary according to the morphological analysis_. Such characteristic may be at the origin of the grain boundaries electrical conductivity mechanism change at low temperatures.

Cobalt nanoparticles added Co_x/Cu_0.5Tl_0.5Ba₂Ca₂Cu₃O_10-δ superconducting composites were synthesized by solid-state reaction method and their superconducting properties were reported. The samples exhibit an orthorhombic crystal structure and the volume of the unit cell decreases with the addition of cobalt nanoparticles, indicating that Co⁺³ ion diffuses from the intergranular region into the unit cells. The suppression of the onset of superconductivity and magnitude of diamagnetism is observed in AC-susceptibility measurements showing magnetic scattering from the charged particles induced by doped Co⁺³ atoms into the unit cell. The doping of unit cells with Cobalt nanoparticles from the inter-grain regions is confirmed by a shift in the peak position and intensity of various oxygen modes in FTIR absorption measurements. Excess conductivity analysis of conductivity data has shown an increase in the coherence length along the c-axis, the Fermi velocity of the carriers, and the energy required to break the Cooper-pairs with the addition of Co nanoparticles. The observed increase in the values of these parameters is likely associated with an increase in the density of charge carriers in the conducting copper oxide planes. It is suggested to be arising from the magnetic scattering of Co⁺³ ions diffusing from inter-grain sites in the unit cell. The weak pinning is also witnessed in form of an increase in the London penetration depth and Ginzburg Landau (GL) parameter κ in Co⁺³ enriched samples.

Ultrafine ceramic powders with high tetragonality are the fundamental for the multi-layer ceramic capacitors (MLCCs). In this study, an efficient method of atmospherically hydrothermal assisted solid-state synthesis for ultrafine BaTiO₃ particles is presented. The BaTiO₃ nanopowders with homogeneous distribution, a mean particle size ~ 260 nm and high tetragonality of 1.0095 were obtained by at the optimal parameters of hydrothermal time of 6 h, Ba(OH)₂·8H₂O/BaCO₃ = 0.25/0.75 and calcination temperature of 1000 ^oC. XRD and HRTEM analyses revealed a “core-shell” structure of TiO₂@BaTiO₃ formed in the first-step hydrothermal process, which reduces the diffusion distance between BaCO₃ and TiO₂, resulting in a lower calcination temperature at the second-step solid-state reaction. Compared with pure hydrothermal and solid-state reaction processes, the atmospherically hydrothermal assisted solid-state synthesis in this study shows larger ability for improving the particle size distribution and the tetragonality, reducing defects of BaTiO₃ particles. In particular, the grain size, sintering density, and dielectric constant at the Curie temperature of BaTiO₃ ceramics are 1.93 μm, 98%, and 7066, respectively. In the solid-state reaction stage, the lattice diffusion distance from BaO to TiO₂ tends to decrease due to the formation of BaTiO₃ shells, thus, high tetragonal and relatively small particle size of BaTiO₃ powder was synthesized. This work presents a method for preparing ultrafine BaTiO₃ powders with large tetragonality for MLCCs.

The preliminary structural and frequency-temperature dependence of dielectric and electrical characteristics of Ba/Zr modified Bismuth ferrite(BiFeO₃) i.e.(Bi_1-xBa_x)(Fe_1-xZr_x)O₃; x = 0.05, 0.1, 0.15, 0.20 at room temperature have been reported. The samples are produced in a perovskite rhombohedral structure, according to the X-ray diffraction pattern and analysis of room temperature XRD data. The SEM photographs are useful for the micro-structural view of the synthesized compounds. Dielectric and electrical characteristics across a wide temperature range 25 °C to 300 °C at different frequencies ranging from 1 kHz to 1 MHz have provided many important results including dielectric dispersion, conduction mechanism, relaxation process and ferroelectricity of the prepared samples. The contributions of grains and grain boundaries towards the net resistance and capacitance of the samples are found from the Nyquist plots. The types of conduction mechanism have been studied from ac-conductivity study of the samples. The Ohmic behaviour is verified by the J–E characteristics of the prepared samples, which have a slope closer to 1. The electrical polarization study through hysteresis loops at room temperature confirms the ferroelectric behavior of the studied materials. According to the experimental results obtained here, the synthesized materials could be beneficial as electronic components in the electronic industries.

In this work, it was aimed to synthesize and characterize rare earth metal-free cerium-based electrolytes that might be used in solid oxide fuel cells (SOFCs) by doping calcium, strontium, or magnesium to CeO₂. For this purpose, CeO₂, Ca_xCe_(1-x)O_(2−δ) (0.16 ≤ x ≤ 0.24), Sr_xCe_(1-x)O_(2−δ) (0.02 ≤ x ≤ 0.08) and Mg_xCe_(1-x)O_(2−δ) (0.07 ≤ x ≤ 0.13) were prepared by using citrate-nitrate combustion method. The solubility limits, microstructural and physical properties of the samples were characterized with XRD, SEM, TG-DTA and impedance analysis. It was found that all samples were in fluorite structure similar to the undoped ceria. The solubility limits of Ca²⁺, Sr²⁺ and Mg²⁺ were 21%, 6% and 12% (by mole) respectively based on XRD analysis results. The relative densities of sintered pellets at 1400 °C were more than 90%. Electrochemical impedance spectroscopy analysis, in which the ionic conductivities of the samples were measured, revealed that the Ca_0.2Ce_0.8O_2-δ (CCO20) sample sintered at 1400 °C showed the highest ionic conductivity value of 4.47 x10^-2 S.cm⁻¹ at 800 °C. It was determined that the O^2- ion conductivity decreased with the order of Ca²⁺ ≈ Sr²⁺ >> Mg²⁺. Conductivities increased with increasing dopant ratio, reached a maximum below the ratios of solubility limits, and then decreased. The obtained results showed that Ca or Sr doped electrolytes prepared by the citrate-nitrate method can show ionic conductivities close to the state-of-the-art Sm doped Ceria electrolytes. It has been determined that Mg doping is quite ineffective.

The preparation of CuCo₂O₄ material with a suitable phase structure and grain size can improve its lithium storage performance. In this paper, CuCo₂O₄ hexagonal nanocrystal were successfully obtained by molten salt modified urea combustion method. Compared with the traditional high temperature solid state methods such as combustion method, rheological phase method and precipitation method, this method maintains the advantage of simple operation, and the particle size of the sample is smaller. The effect of heat treatment temperature on the lithium storage performance of CuCo₂O₄ was also studied systematically in this paper. The result shows that 800 ℃ is the best heat treatment temperature for CuCo₂O₄, and the sample synthesized by the molten salt urea combustion method exhibited the best electrochemical properties with a specific capacity of 705 mA h g^-1 after 100 cycles under a constant current of 200 mA g^-1 in the voltage range of 0.01-3 V. Therefore, a new strategy of high temperature solid state preparation has been developed in this paper, and the CuCo₂O₄ synthesized by this method is a promising anode material for lithium ion battery application.

The present study aimed to verify the experimentally obtained results by exploring the several properties of the material (i.e. magnetic, structural, and direct current (DC)-electrical properties). Trivalent rare-earth element samarium (Sm³⁺)doped barium spinel ferrites BaSm_xFe_2−xO₄ for compositions with the following x values: 0, 0.025, 0.05, 0.075, and 0.1 were subjected to the sol-gel procedure for processing. All of the samples, according to X-ray diffraction (XRD) investigation, developed a structure with a single phase that is cubic. The structural parameters, including lattice constants, crystalline size (nm), densities (bulk and X-ray), and unit-cell volume, were observed. The semiconductor natureof the prepared materials was demonstrated by the use of two-probe tests to estimate DC resistivity (ρ_dc), Curie temperature (T_c). Ferromagnetic materials’ properties resemble remenance (M_r), coercivity (H_c), saturation magnetization (M_s), and changes that resulted from the insertion of Sm³⁺ was injected in the M-H condition (magnetization-applied field) loops are assigned to each individual nanoparticle. It’s been discovered that the evolution of the anisotropic constant is kind of analogous to those of the coercivity. The current synthesized barium ferrites have been confirmed to really be useful as in manufacturing of high-density magnetic storage applications.